On Mon, Feb 20, 2017 at 12:30:11PM +0000, Mark Rutland wrote:
> Currently we BUG() if we see a HSR.EC value we don't recognise. As
> configurable disables/enables are added to the architecture (controlled
> by RES1/RES0 bits respectively), with associated synchronous exceptions,
> it may be possible for a guest to trigger exceptions with classes that
> we don't recognise.
>
> While we can't service these exceptions in a manner useful to the guest,
> we can avoid bringing down the host. Per ARM DDI 0406C.c, all currently
> unallocated HSR EC encodings are reserved, and per ARM DDI
> 0487A.k_iss10775, page G6-4395, EC values within the range 0x00 - 0x2c
> are reserved for future use with synchronous exceptions, and EC values
> within the range 0x2d - 0x3f may be used for either synchronous or
> asynchronous exceptions.
>
> The patch makes KVM handle any unknown EC by injecting an UNDEFINED
> exception into the guest, with a corresponding (ratelimited) warning in
> the host dmesg. We could later improve on this with with a new (opt-in)
> exit to the host userspace.
>
> Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> Cc: Dave Martin <dave.martin@xxxxxxx>
> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> arch/arm/include/asm/kvm_arm.h | 1 +
> arch/arm/kvm/handle_exit.c | 19 ++++++++++++-------
> 2 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_arm.h b/arch/arm/include/asm/kvm_arm.h
> index e22089f..a3f0b3d 100644
> --- a/arch/arm/include/asm/kvm_arm.h
> +++ b/arch/arm/include/asm/kvm_arm.h
> @@ -209,6 +209,7 @@
> #define HSR_EC_IABT_HYP (0x21)
> #define HSR_EC_DABT (0x24)
> #define HSR_EC_DABT_HYP (0x25)
> +#define HSR_EC_MAX (0x3f)
>
> #define HSR_WFI_IS_WFE (_AC(1, UL) << 0)
>
> diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
> index 4e40d19..96af65a 100644
> --- a/arch/arm/kvm/handle_exit.c
> +++ b/arch/arm/kvm/handle_exit.c
> @@ -79,7 +79,19 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
> return 1;
> }
>
> +static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +{
> + u32 hsr = kvm_vcpu_get_hsr(vcpu);
> +
> + kvm_pr_unimpl("Unknown exception class: hsr: %#08x\n",
> + hsr);
> +
> + kvm_inject_undefined(vcpu);
> + return 1;
> +}
> +
> static exit_handle_fn arm_exit_handlers[] = {
> + [0 ... HSR_EC_MAX] = kvm_handle_unknown_ec,
Cool stuff, didn't know you could do this in C.
> [HSR_EC_WFI] = kvm_handle_wfx,
> [HSR_EC_CP15_32] = kvm_handle_cp15_32,
> [HSR_EC_CP15_64] = kvm_handle_cp15_64,
> @@ -98,13 +110,6 @@ static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
> {
> u8 hsr_ec = kvm_vcpu_trap_get_class(vcpu);
>
> - if (hsr_ec >= ARRAY_SIZE(arm_exit_handlers) ||
> - !arm_exit_handlers[hsr_ec]) {
> - kvm_err("Unknown exception class: hsr: %#08x\n",
> - (unsigned int)kvm_vcpu_get_hsr(vcpu));
> - BUG();
> - }
> -
> return arm_exit_handlers[hsr_ec];
> }
>
> --
> 1.9.1
>
Reviewed-by: Christoffer Dall <cdall@xxxxxxxxxx>
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
